The present invention relates to a syringe, and more particularly to a safety syringe for preventing contamination, fear of contamination and physical injury by "needle stick" by the syringe needle after use and/or for preventing reuse of the syringe.
In order to minimize the risk of contamination from a used syringe, it is common practice for used syringes to be deposited into heavy duty plastic bins which cannot be pierced by the needles. The bin and contents are then moved to a disposal facility at which they are incinerated. This means of disposal is of limited effect as it does not eliminate "needle stick" risk between needle use and disposal. Current disposal methods are also relatively expensive.
Numerous attempts have been made to design an acceptable syringe in which, after use, the needle is withdrawn into the body of the syringe and retained there in some manner. These designs are all directed to the same end of covering the needle after use to prevent inadvertent "needle stick" injuries with their attendant risk of cross-infection and to prevent reuse of the syringe. In many of these prior art arrangements the withdrawal of the needle into the body is entirely manual and requires the syringe user to remember to make some deliberate relative movement, normally between the plunger and the body, to effect withdrawal of the needle into the body of the syringe. Proposals have been made, as in Australian Patent Specifications 593,513, 594,634 and 35,676/89, to induce automatic withdrawal of the plunger into the body by the use of a helically coiled spring. This necessitates the use of additional and costly parts in the syringe and complicates its assembly.
Applicant's U.S. patent application Ser. No. 07/720,499, filed July 1991, now U.S. Pat. No. 5,215,533 is directed to a safety syringe in which a vacuum generated by depression of the plunger causes the plunger and a needle holder to which it has become attached to be drawn securely back into the barrel of the syringe. The present application is directed to a braking means to control retraction of the plunger and the needle holder into the barrel, to stop means to prevent premature engagement of the plunger with the needle holder, and to connection means for connecting the plunger to the needle holder.